Recent Submissions

  • Size composition of the catches of the pink shrimp Penaeus duorarum notialis in the shrimp fishery of Sierra Leone

    Scott, R.B.S.; Institute of Marine Biology & Oceanography, Fourah Bay College, University of Sierra Leone (1978)
    Measurements were taken of size distribution of P. d. notialis collected off Sierra Leone over a period of six months from October 1977 to March 1978. From the frequency distribution curves it is observed that the curves for male shrimps show only one or two major modes, which show prominence between 12.5 and 14.1 cm of total length. Females mostly exhibited size groups with three or four different length ranges and occasional occurrence of 1 to 5 modes. These size groups were observed to show continuous changes. No one group could be said to be permanent. The point of entry into the fishery of male shrimps was found to be at an average total length of 10.5 cm, while females did so at 11 cm. Sex ratios in the different samples were usually 1:1 but in one case the males were more numerous by 2:1 and in four other samples females were significantly preponderent. These departures from the 1:1 ratio may have been artificially created by sorting of the catches on board the ships.
  • Marine biology of the Sierra Leone River Estuary. 1. The physical environment

    Findlay, I.W.O.; Institute of Marine Biology & Oceanography, Fourah Bay College, University of Sierra Leone (1978)
    The Sierra Leone River Estuary is a relatively young drowned river valley, it is shallow except for a deep channel which passes close to the Freetown shoreline. The upper reaches merge into a network of creeks and channels fringed by large areas of mangrove swamps. It is a tidal estuary of the semi-mixed type with the saline oceanic water entering it on a diurnal cycle. The climate of Sierra Leone is marked by a very distinct change between a very wet rainy season and a dry season. The tidal range of the Estuary (spring 3.03m; neap 2.28m) does not impede normal use of the harbour. The tidal variations can be felt as far as 42 miles inland along the water courses of the Sierra Leone River and its tributaries. The volume of fresh water entering the Estuary is large during the rainy season and greatly reduced during the dry season. Consequently there is a marked fall in salinity during the rainy season and higher salinities due to the marine influence prevailing during the dry season. The nature of the shores and bottom, the hydrography and chemistry of the estuarine system have been outlined in relation to the prevailing climatic conditions.
  • Making kippers from local herring (Sardinella spp.) smoke-cured in the Torry Kiln

    Mason, E.D.C.; Institute of Marine Biology and Oceanography, Fourah Bay College, University of Sierra Leone (1978)
    (Sardinella) are available all year round in Sierra Leone. The best time to use them for baiting herrings is during the dry season when they are fattest and feeding well. The most common method of processing herring locally is hot smoking to give either soft, moist and cooked product or a dry, brittle product with very low moisture content. The author describes a curing method intended to add variety to the types of products that can be obtained from local herring. It is only mildly preservative, the product cannot be kept more than 24 hours without refrigeration. Particular attention is paid to the source and quality of the raw material used, and the processing method is detailed with attention to washing, splitting, brining, smoking, and the application of the Torry fish smoking kiln to the process.
  • The effect of sublethal concentration of DimilinR (TH6040) on the larval development of the mud-crab Rhithropanopeus harrisii (Gould)

    Wilson, J.E.H.; Institute of Marine Biology & Oceanography, Fourah Bay College, University of Sierra Leone (1978)
    Sublethal DimilinR (insecticide) concentration significantly decreased the percentage survival of larval R. harrisii . This decrease was marked at low salinities, when it may have become toxic. This was true for both 25 and 30 C. Duration of larval development did not seem to be affected by sublethal DimilinR concentrations even in extremely low or high salinities. High temperature, however, shortened the time of development. No anatomical abnormality was observed. These findings are only tentative as more replicates of the experiments are needed before definite conclusions can be reached. It will be desirable to work with more salinity-temperature combinations to get a complete picture of sublethal effects under different environmental conditions.
  • (Report of the) Institute of Marine Biology and Oceanography, Fourah Bay College, University of Sierra Leone

    Okera, W. (Institute of Marine Biology & Oceanography, Fourah Bay College, University of Sierra LeoneFreetown (Sierra Leone), 1976)
    Details are given of the Institute and its activities, in particular the research projects being undertaken. These include studies on the marine molluscs of Sierra Leone, the cockle fishery, a preliminary investigation on the fouling organisms affecting the raft-cultured oyster populations, larval oyster ecology in relation to oyster culture, preliminary studies on the reproductive cycle of the mangrove oyster (Crassostrea tulipa), and catch composition of fishes taken by beach-seines at Lumley (Freetown). Records of the west African manatee (Trichechus senegalensis) are noted.
  • Synopses of research on shrimps: 1. The common shrimp species of Sierra Leone's coastal waters: their distribution, abundance and size composition

    Okera, W.; Chaytor, D.E.B. (1978)
    The authors present quantitative information on the shrimp resources of Sierra Leone waters. Four of the nine species present have been studied, of which Paenaeus duorarum notialis is dominant in the fishery. Synoptic surveys were undertaken in June 1977, and March 1978, to determine the abundance of the shrimp stock on the inshore shelf. The temperature-salinity-depth curves for the fishing ground show the existence of three water masses. The majority of fish caught were sciaenids, with some sparids also being taken. Detailed discussion of distribution and abundance of individual species of shrimp is given. The surveys have shown that the Banana Islands are the most productive shrimp grounds in the country, and the authors believe that they can support a viable shrimp industry for several years to come at present rates of exploitation
  • Studies on the condition factor of the Sierra Leone mangrove oyster (Crassostrea tulipa)

    Wellesley-Cole, C.; Kamara, A.B. (1978)
    Sierra Leone is a tropical country where water temperatures are high throughout the year. Consequently the local oysters tend to spawn the year round, with one or two spawning peaks. The condition of such tropical oysters may not be as high as those oyesters in temperate countries since the stored glycogen is regularly utilized to form gonads. A high condition factor value indicates that the oysters have accumulated glycogen and or gonads, whereas a low condition factor value indicates that the oysters have spawned and are in the process of accumulating glycogen, which may later be utilized for gonad development. In oyster culture, condition factor studies may be supported by plankton and oyster spat settlement studies in the culture area. These studies give an indication of when oyster larvae and spat settlement are at their peak values. In Sierra Leone studies of the plankton and spat settlement are undertaken every week throughout the year. Conditions factor is obtained from the ratio weight of dry (oyster) meat x 1000/internal volume. Detailed condition factor values are shown in relation to salinity at two stations. Condition factor declines with reducing salinity, which principally occurs during the rainy season. The best times to collect spat are May to June and September to October
  • Some data on landings of pelagic fish by the artisanal fishermen near Freetown during January-December 1978

    Brainerd, T.R. (1978)
    Pelagic fish (except for tuna) are landed in Sierra Leone mainly by the artisanal fishermen. The two most important species are Sardinella and Ethmalosa.Deep-sea species are normally exploited by purse seiners of foreign countries. The landings of artisanal fishermen largely comprise Sardinella eba.Landing data for Sardinella landed at Tombo and Goderich, and for Ethmalosa at Tombo, are presented in tabular form. Collection methods are described, with a definition of the unit of fishing effort, and a description of the gear used.The landing data are discussed with particular attention to fishing effort, catch per unit effort, and price per ton
  • A key for the identification of West African marine Gastropoda (excluding the nudibranch sea-slugs) and Bivalvia

    Okera, W.; Institute of Marine Biology & Oceanography, Fourah Bay College, University of Sierra Leone (1977)
  • A list of the estuarine and marine fishes and some shellfishes of Sierra Leone, with their common names in either Krio or English

    Kamara, A.B.; Institute of Marine Biology & Oceanography, Fourah Bay College, University of Sierra Leone (1977)
  • A list of the freshwater fishes and some shrimps of Sierra Leone with their vernacular names in Mende, Temne and Limba

    Iscandari, N.; Institute of Marine Biology & Oceanography, Fourah Bay College, University of Sierra Leone (1977)
  • Survey of the shrimp stocks of the Sierra Leone inshore shelf : a summary report outlining objectives, observations and recommendations on the status of the Sierra Leone shrimp fishery

    Chaytor, D.E.B.; Okera, W.; Institute of Marine Biology & Oceanography, Fourah Bay College, University of Sierra Leone (1977)
    This report gives the species and catch-rates per hour of some commercial shrimp species caught in the course of a short survey of inshore shelf fishing grounds. Species seen in significant quantities were: Parapenneopsis atlantica, Parapenaeus longirostris, Penaeus kerathurus and Penaeus duorarum notialis
  • A key for the identification of economically important West African marine and freshwater shrimp-like crustaceans

    Okera, W.; Institute of Marine Biology & Oceanography, Fourah Bay College, University of Sierra Leone (1977)
  • Biology of the mullet species occurring in the estuaries of Freetown Peninsula

    Wilson, J.E.H.; Institute of Marine Biology & Oceanography, Fourah Bay College, University of Sierra leone (1977)
    This brief paper gives some notes on the geographical distribution and salinity tolerances of some Mugil species occurring in the Black-Johnson estuary, Sierra Leone
  • Report on the physical, bacteriological and biochemical analyses of seawater samples collected off existing sewage outfalls in the Sierra Leone River Estuary

    Institute of Marine Biology and Oceanography, Fourah Bay College, University of Sierra Leone (1980)
    The studies reported were undertaken as part of a wide environmental feasibility study for the establishment of a modern sewage system in Freetown. The aim of this part of the study was to determine whether the hydrological regime of the Sierra Leone River Estuary would permit the large-scale introduction of sewage into the estuary without damaging the environment. The important factors were whether: 1) there would be sufficient dilution of the sewage; 2) fleatable particles or other substances would create significant adverse effects in the estuarine ecosystem. The outfall sites are described together with the sampling stations, methods and analyses. Results include: 1) T/S profiles; 2) chemical analysis of the water. A review of literature on the Sierra Leone River Estuary is included which provides information on the plankton, benthos and fisheries. Results suggest that at certain points where local circulations occur it would be inadvisable to locate untreated sewage outfalls. Such points are frequently observed in small embayments. These studies have been of short duration but the data can serve as baseline for more extended investigations which would give a more complete picture of the seasonal patterns in the estuary.